The role of the thalamus in brain function has been somewhat neglected until relatively recently. This is particularly true of one of its most prominen components, the pulvinar. The goal of this proposal is to understand the functional subparts of the pulvinar and how they relate to different visual cortical areas. We argue that one of the reasons there has been so little progress in understanding the role of the pulvinar is that basic information is missing about its properties and connections with well-defined areas. Building on our recent work investigating the primate pulvinar, the key to functionally parsing the pulvinar is to use the retinotopic maps in pulvinar as the starting point just as retinotopic maps in cortex define functional areas in cortex. There are two well-defined retinotopic pulvinar maps that exist in the inferior and lateral pulvinar of all studied primates. To date, we still know very little abut their functions, and the differences between these two maps. We hypothesize that the two maps are biased to connect to dorsal and ventral stream visual cortical areas. These biases should allow separate cortical areas to purpose the two retinotopically defined mapped zones in distinct ways. We plan to test this hypothesis in the form of two aims. In aim 1 we propose three anatomical studies to define the details of the cellular, axonal and connectional differences between the two pulvinar maps as these relate to cortical visual areas V1, V2, V3, DL/V4 and MT/V5. In aim 2 we propose three physiological studies designed to compare the receptive field properties and their organization between the two retinotopically defined maps. We believe, taken together, these studies will provide the keys to parsing the primate pulvinar which, in turn, will provide the necessary tools to understand the functional significance of pulvinar and provide insights into thalamic control of visual information flow.